JPS5827352B2 - Manufacturing method of ion exchange membrane with electrode layer attached - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ion exchange membrane with an electrode layer attached thereto, in particular an alkali chloride aqueous solution, in which a gas-permeable porous electrode layer is provided in close contact with the ion exchange membrane surface. This invention relates to a method for producing an ion exchange membrane with an electrode layer attached, which is suitable for electrolysis.

In recent years, from the viewpoint of pollution prevention, the method for obtaining caustic alkali and chlorine by electrolyzing an aqueous alkali chloride solution has been replaced by the diaphragm method instead of the mercury method, and a method using an ion exchange membrane for the purpose of obtaining even higher purity and highly concentrated caustic alkali. has been put into practical use.

On the other hand, in this type of electrolysis, from the perspective of energy saving, it is imperative to keep the electrolytic chamber as low as possible. The so-called SPE (Solid Po
1yner Electrolyte) type alkali chloride electrolysis (for example, JP-A-53-52297, JP-A-52-78788) is known.

This is a method that allows electrolysis to be carried out at a much lower voltage than before because it reduces the electrical resistance of the electrolytic solution and the bubbles caused by the generated hydrogen and chlorine gas, which were previously thought to be unavoidable in this type of technology. This is an excellent method.

By the way, in the SPE type ion exchange membrane electrolyzer, the contact between the gas-permeable porous electrode layer and the ion exchange membrane surface is an important point that affects the performance of the device, and the thickness of the electrode layer is If the contact between the electrode layer and the ion exchange membrane is non-uniform, or if the contact between the electrode layer and the ion exchange membrane is not sufficient, part of the electrode layer may easily separate, resulting in an increase in sliding voltage or the presence of gas or other gas at the contact interface. Due to the accumulation of excess liquid, the sliding current increases, and the intended advantages of the device are reduced or not obtained.

The present invention employs a novel construction means for the contact between the gas permeable porous electrode layer and the ion exchange membrane in this type of ion exchange membrane electrolysis device, thereby creating a uniform thickness on the ion exchange membrane surface. A novel method for manufacturing an ion exchange membrane with an electrode layer attached thereto is provided, which incorporates an ion exchange membrane provided to sufficiently adhere the electrode layer.

That is, the present invention prints a paste containing an electrode powder and a hydrophobic polymer on the surface of an ion exchange membrane using a screen printing method, and then thermally presses the material to form a porous electrode that is permeable to gas and liquid. A method of manufacturing an ion exchange membrane with an electrode layer attached thereto, in which a layer is provided in close contact with the surface thereof.

In the screen printing used for adhering the electrode layer to the ion exchange membrane surface of the present invention, a paste containing electrode powder and a hydrophobic polymer is used.

As the electrode, any material can be used as long as it is used as an anode or a cathode. For example, as an anode, one or more of platinum group metals such as platinum, ruthenium, rhodium, and iridium and their oxides can be used. be.

As the cathode, for example, iron, nickel, stainless steel, thermal decomposition products of fatty acid nickel, Raney nickel, stabilized Raney nickel, carbonyl nickel, and carbon powder supporting a platinum group metal are used.

The electrode is preferably added to the paste as a powder with a particle size of 0.01-300μ, especially 0.0-100μ.

The hydrophobic polymer acts as a binder between the electrodes and between the electrodes and the ion exchange membrane, and is preferably a fluorinated polymer, particularly a perfluorinated hydrocarbon such as polytetrafluoroethylene or polyhekifluoroethylene. Polymers are used.

The hydrophobic polymer preferably has a particle size of 0.1 to 500 microns, particularly 0.1 to 100 microns, and is preferably sufficiently dispersed in the paste.

In order to improve dispersion, a required amount of surfactant, preferably a long-chain hydrocarbon or fluorinated hydrocarbon, can be added.

The content of the electrode powder and hydrophobic polymer in the paste is also related to the electrode performance, but the former is preferably 20 to 9
5φ, especially 40-90%, the latter preferably 0
．． The price ranges from 1 to 80 yen, especially from 1 to 60 yen.

The viscosity of the paste containing the electrode powder and the hydrophobic polymer is suitably controlled to preferably 1 to 105 poise, particularly 10 to 10' poise for screen printing.

For this reason, it is possible to control the particle size and amount of the electrode powder and hydrophobic polymer, as well as the amount of water as a medium, but preferably a viscosity adjusting substance is added to control the viscosity within the above range. can.

Examples of viscosity adjusting substances include celluloses such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, and cellulose, which are water-soluble viscous substances that can dissolve in water over time, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, Polymethyl vinyl ether and the like are used.

Since these are water-soluble substances, they do not impede the performance as an electrode.

In addition, casein, polyacrylamide, etc. can be used as the viscosity adjusting substance, as long as it is a substance that does not deteriorate or corrode during the electrode layer formation process or during use as an electrode layer and does not impair electrolytic performance. .

The paste-like material is printed and adhered directly to the surface of the ion exchange membrane by screen printing.

For screen printing, a known method is adopted, but the screen used in the present invention preferably has a printing density of 10 to 2400.
A mesh, especially a 150-100 mesh, is suitable, and the thickness is preferably 2 to 4μ, especially 300μ to
8μ is appropriate.

If the mesh number is too large, the screen will become clogged, resulting in uneven printing; if the mesh number is too small, too much paste will be deposited.

On the other hand, if the thickness is too large, printing will be uneven, and if it is too small, it will not be possible to print a predetermined amount.

A screen mask is used to provide an electrode layer of an appropriate size and shape on the surface of an ion exchange membrane, and its shape is formed by cutting out the shape of the electrode layer to be formed on the membrane surface. Usually, the thickness is preferably 3 to 500 μm.

The materials for the screen and screen mask need only have sufficient strength, and for example, stainless steel, Tetron, nylon, or epoxy resin are used, respectively.

A screen with a screen mask attached is placed on the ion exchange membrane on which the electrode layer is formed, and the paste is supplied onto the screen and printed while applying pressure with a squeegee to form the screen mask. An electrode layer having a shape excluding the above is formed on the ion exchange membrane surface.

The thickness of the electrode layer on the ion exchange membrane surface depends on the screen thickness, paste viscosity, number of screen meshes, etc., so the thickness of the electrode layer is preferably 1 to 5.
It is preferable to adjust the thickness of the screen, the viscosity of the paste, the number of meshes of the screen, etc. so that the thickness becomes 00μ, particularly 1 to 300μ.

Furthermore, the distance between the screen plate and the ion exchange membrane during screen printing, the material of the squeegee, and the pressure applied to the squeegee are also related to the physical properties, thickness, and uniformity of the electrode layer formed on the ion exchange membrane surface. In order to obtain a predetermined value, for example, the distance between the screen plate and the ion exchange membrane should be set to a predetermined distance depending on the type and viscosity of the paste, and the squeegee should have straight edges and a hardness that matches the viscosity of the paste. It is preferable to select the material and keep the applied pressure of the squeegee constant.

In this way, an electrode layer having a uniform thickness and high adhesion is formed on one or both surfaces of the ion exchange membrane, but it is preferable to press the electrode layer against the membrane surface under pressure if necessary.

The suppression is preferably between 100 and 300°C, especially at 110°C.
Preferably 5-1000 kg/under heating at ~250°C
cyyt, particularly those pressed under 20 to 500 kg/i are preferred.

By doing so, the ion exchange membrane and the electrode layer can have a structure in which they are in even closer contact.

The electrode layer thus formed on the ion exchange membrane surface needs to be porous and gas permeable, preferably with an average pore diameter of 0.01 to 50μ, particularly 0.1 to 50μ.
30 μ, porosity 30 to 99φ, especially 40 to 98 coefficient, air permeability coefficient lXl0-' to 1 mol/cyrY, mi
n, c+ytH, 9, especially 1 x 10-4 to 1 x 10-
1 mol/cyyt, min, CrfLH, @
It is preferable that 0).

The physical properties of these electrode layers, such as average pore diameter, porosity, and air permeability coefficient, are mainly influenced by the shape, size, and amount of the electrode powder used to form the paste, as well as the amount of the hydrophobic polymer. By selecting this, the physical properties of the electrode layer can be controlled.

The ion exchange membrane on which the electrode layer of the present invention is formed is made of a polymer containing a cation exchange group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a phenolic hydroxyl group. For example, a vinyl monomer such as tetrafluoroethylene or chlorotrifluoroethylene and a perfluorinated vinyl monomer having a cation exchange group such as a sulfonic acid, carboxylic acid, or phosphoric acid group, or a reactive group that can be converted into a cation exchange group. A copolymer of is preferred.

Also usable are trifluoroethylene membrane polymers into which ion exchange groups such as sulfonic acid groups have been introduced, and styrene divinylbenzene into which sulfonic acid groups have been introduced.

Among these, it is preferable to use monomers that can form the following polymerized units (A) and (D), respectively.

where X is F, CA, H or -CF3 and X/ is X
or CF3(CF2)m, m is 1 to 5, and Y
is selected from the following:

x, y, and z are all 1 to 10, and Z and Rf are -F or C1.

perfluoroalkyl group.

A is -COOH, -CN, -COF. COOR1,-
Indicates a functional group that can be converted to -COOH by hydrolysis or neutralization, such as COOM and -CONR2R3.

R1 is an alkyl group of 01 to 1o, M is an alkali metal or a quaternary ammonium group, and R2 and R3 are H or C1
~1o alkyl group.

In the present invention, the concentration of carboxylic acid groups in the film per gram of dry resin made of these copolymers is 0.5 to 2.5.
When using a fluorine-containing cation exchange membrane having a milliequivalent weight, particularly 1.0 to 2.0 milliequivalents, the objects of the present invention can be achieved sufficiently and stably, and particularly in terms of sustainability and durability. Therefore, it is preferable.

In order to produce the above-mentioned fluorine-containing copolymer, it is possible to use one or more of the above-mentioned monomers and further copolymerize a third monomer, thereby modifying the resulting membrane.

The cation exchange membrane used has a thickness of 20 to 500μ,
Preferably, it is appropriate to make it 50 to 400μ.

When the ion exchange group possessed by the cation exchange membrane is not a carboxylic acid group itself but a functional group that can be converted into the group,
Upon use, these functional groups are converted into carboxylic acid groups by appropriate treatment.

For example, -CN, -COF, -COOR,. -COO
M, -CONR2R3 (M, R, ~R3 are the same as above)
In this case, with an alcoholic acid or alkali solution,
It is converted into a carboxylic acid group by hydrolysis or neutralization, and when the functional group is a double bond, it is converted into a carboxylic acid group by reacting with COF2.

In addition, when using a cation exchange membrane having such a carboxylic acid group, the printing and pressure bonding of the electrode layer on the ion exchange membrane surface by screen printing described above should be performed when the exchange group is of the formula -COOL (
L is hydrogen or a lower alkyl group), and when the above-mentioned heating and pressure bonding is performed, the adhesion between the electrode layer and the ion exchange membrane is even better, and the electrode layer adheres to the ion exchange membrane with excellent performance. A membrane is obtained.

Furthermore, the above-mentioned cation exchange resin membrane may be formed using an olefin polymer such as polyethylene or polypropylene, preferably a fluorine-containing polymer such as polytetrafluoroethylene or a copolymer of ethylene and tetrafluoroethylene, during membrane formation, if necessary. Alternatively, fabrics made from these polymers such as cloth, net, nonwoven fabric, porous film, metal wire, net, perforated plate, etc. can be used as a support. It is also possible to reinforce the membrane.

In addition, when such a mixture or support is used, the weight of the resin constituting the mixture or support is not included in the resin weight when calculating the exchange group concentration per dry resin.

To produce caustic alkali by electrolyzing an aqueous alkali chloride solution using an electrolytic layer using an ion exchange membrane with an electrode layer attached thereto obtained according to the present invention, an aqueous alkali chloride solution is placed in the anode chamber side partitioned by an ion exchange membrane with an electrode layer attached, Normal water is supplied to the cathode chamber side to perform electrolysis.

The alkali chloride used is usually table salt, but
Other chlorides of alkali metals such as potassium chloride and lithium chloride make it possible to stably and advantageously produce the corresponding caustic alkalis from their aqueous solutions over a long period of time.

Next, the present invention will be explained by examples.

Example-1 1 part of carboxymethyl cellulose (hereinafter abbreviated as CMC) and 5 parts of polyvinyl alcohol (hereinafter abbreviated as PVA) were dissolved in 95 parts of water at a temperature of 80°C, and the wire material thus prepared was To the mixture, an aqueous dispersion containing 60 parts by weight of polytetrafluoroethylene (hereinafter abbreviated as PTFE) with a particle size of 1 μm or less and 200 parts of platinum black powder with a particle size of 25 μm or less were added and kneaded to obtain Paste 1.

The paste 1 was mixed with a mesh number of 200. Using a printing plate with a 60μ thick stainless steel screen and an 8μ thick screen mask underneath, and a polyurethane rubber squeegee, the ion exchange capacity of the printing substrate was 1.
．． 45meq/g dry resin, polytetrafluoroethylene with thickness 250μ and CF2=CFO(CF2)3
Screen printing was performed on one side of an ion exchange membrane made of a copolymer of C00CH3 to a size of 20 cIrL x 25.

The printed layer obtained on one side of the ion exchange membrane was dried in air to solidify the paste and serve as an anode.

The resulting anode had a thickness of about 14μ and a platinum content of 3μ/cv.
i was included.

On the other hand, PTFE with a particle size of 1μ or less was added to the above wire rod.
After dissolving and removing 35 parts of an aqueous dispersion containing 0 weight φ and the aluminum of the Raney alloy with an alkali, washing with water and drying, 200 parts of partially oxidized stabilized Raney nickel powder with a particle size of 25μ or less was added. Then, paste 2 was obtained by kneading.

The paste 2 was printed on the other side of the ion exchange membrane using a squeegee and a printing plate with a stainless steel screen with a mesh count of 200 and a thickness of 80μ under which a screen mask with a thickness of 30μ was applied. The printing layer is dried inside the
The paste was solidified to form a cathode.

The resulting cathode has a thickness of 35μ and a nickel content of 7my/-
It was included.

After that, the temperature was 150℃ and the molding pressure was 25kg/cril.
After the printed layer was pressure-bonded to the ion membrane under the following conditions, it was immersed in a caustic soda aqueous solution of 25 weight φ at 90° C. for 16 hours to hydrolyze the ion membrane and elute CMC and PVA.

In addition, a platinum wire mesh was brought into pressure contact with the cathode and anode as current collectors, and while supplying a 5N NaCl aqueous solution to the anode chamber and water to the cathode chamber, the sodium chloride concentration in the anode chamber was adjusted to 4N, and the cathode The concentration of caustic soda in the liquid is 35 weight φ
Electrolysis was carried out while maintaining the temperature, and the following results were obtained.

Further, the current efficiency for producing caustic soda at a current density of 20 people/dm2 was 95 μm.

Further, when electrolysis was carried out for one month at a current density of 20 A/dm2, the sliding voltage was almost constant, and no peeling or falling of the electrode from the ion membrane surface was observed.

Example-2 1 part of CMC was placed in 50 parts of ethylene glycol at a temperature of 100%.
The electrode was brought into close contact with the ion exchange membrane in the same manner as in Example-1, except that the wire rod dissolved in 'C was used, and further, electrolysis was carried out under the same conditions as in Example-1.

The results are shown below. Further, the current efficiency of the caustic soda insect repellent at a current density of 20 A/dm2 was 94φ.

Example-3 10 parts of PVA and 20 parts of polyvinylpyrrolidone were added to 1 part of water.
The electrode was brought into close contact with the ion exchange membrane in the same manner as in Example-1 except that the melted wire was used in 00 parts at a temperature of 80°C, and further electrolysis was carried out under the same conditions as in Example-1. The results are shown below.

Further, the current efficiency for producing caustic soda at a current density of 20 A/dm2 was 94φ.

Example-4 In Example-1, instead of platinum black on the anode, a particle size of 25
The electrode was brought into close contact with the ion exchange membrane in the same manner as in Example 1, except that a powder of platinum black 70 - iridium black 30 (atomic ratio) of less than μ was used, and further under the same conditions as in Example 1. The results of electrolysis are shown below.

Further, the current efficiency for producing caustic soda at a current density of 20 A/dm2 was 94 lines.

Example-5 In Example-1, the anode has a mesh number of 400° and a thickness of 5.
An electrode adhesion membrane was obtained in the same manner as in Example 1, except that the ion exchange membrane was screen printed using a 2μ stainless steel screen printing plate.

The anode was approximately 9μ thick and contained 2μ/− of platinum.

Furthermore, the results of electrolysis performed under the same conditions as in Example 1 are shown below.

Further, the current efficiency for producing caustic soda at a current density of 20 A/dm2 was 94 factors.

Example-6 Example-1 except that the anode paste and cathode paste in Example-1 were changed into the following pastes.
The electrode was brought into close contact with the ion exchange membrane in the same manner as above.

The anode paste was prepared by adding 30 parts of an aqueous dispersion containing 20 weight φ of PTFE with a particle size of 1 μm or less to 70 parts of platinum black powder with a particle size of 25 μm or less, and kneading the mixture.

The paste for the cathode consists of 75 parts of stabilized Raney nickel powder with a particle size of 25 μm or less and 3 parts of PTFE with a particle size of 1 μm or less.
25 parts of an aqueous dispersion containing 0 weight φ was added and kneaded.

Furthermore, electrolysis was carried out under the same conditions as in Example-1.

The results are shown below. In addition, the current density is 20 A/dm2
The current efficiency of caustic soda production was 95%.

Claims (1)

[Claims] 1. A paste-like material containing electrode powder and a hydrophobic polymer is printed on the surface of an ion-exchange membrane using a screen printing method, and then thermally adhered to the surface of the ion-exchange membrane to form a porous material that is permeable to gas and liquid. A method for producing an ion exchange membrane with an electrode layer attached, in which an electrode layer is provided in close contact with the surface of the membrane. 2. The manufacturing method according to claim 1, wherein the paste-like material contains a fluorine-containing polymer as the hydrophobic polymer and has a viscosity of 1 to 105 poise. 3 The mesh number and gauze thickness of the screen are each 10
2400 mesh and 2 mm to 4μ. 4 The electrode layer has an average pore diameter of 0.01 to 50μ and a porosity of 3
0 to 99φ, air permeability coefficient lXl0-5 to 1 molar history α, Hg. 5. Claim 1, wherein the ion exchange membrane is a fluorine-containing cation exchange membrane having a carboxylic acid group or a sulfonic acid group.
, 2.3 or 4 manufacturing method.